A dark-skinned, curly-headed person who identifies as African American may, indeed, have much in his or her history and upbringing to justify that identification. But he or she may also have a white grandparent and several Cherokee ancestors. Thus, returning to the example of glaucoma, it is more important to know a patient's family history than to assess his or her race. And collecting family history ought to mean not only compiling a list of which diseases family members have, but making some attempt to assess common (familial) habits such as diet and life experiences (e.g., first- versus second-generation immigrants, living conditions, or same versus widely varied work experience and geographical locations). Similarly, when the history of passing for white is ignored, those who identify themselves as "white" are assumed to have no ancestral "black blood." Finally, immigration patterns constantly change. A "black" person walking into a Boston, Massachusetts clinic could easily be the child of a recent immigrant from Ethiopia or Brazil who has a genetic makeup as well as cultural and environmental exposures that differ significantly from the descendents of 19th century US slaves from the western coast of Africa.

It is insufficient to state the obvious of Donald Trump: that he is a white man who would not be president were it not for this fact. With one immediate exception, Trump’s predecessors made their way to high office through the passive power of whiteness—that bloody heirloom which cannot ensure mastery of all events but can conjure a tailwind for most of them. Land theft and human plunder cleared the grounds for Trump’s forefathers and barred others from it. Once upon the field, these men became soldiers, statesmen, and scholars; held court in Paris; presided at Princeton; advanced into the Wilderness and then into the White House. Their individual triumphs made this exclusive party seem above America’s founding sins, and it was forgotten that the former was in fact bound to the latter, that all their victories had transpired on cleared grounds. No such elegant detachment can be attributed to Donald Trump—a president who, more than any other, has made the awful inheritance explicit.

His political career began in advocacy of birtherism, that modern recasting of the old American precept that black people are not fit to be citizens of the country they built. But long before birtherism, Trump had made his worldview clear. He fought to keep blacks out of his buildings, according to the U.S. government; called for the death penalty for the eventually exonerated Central Park Five; and railed against “lazy” black employees. “Black guys counting my money! I hate it,” Trump was once quoted as saying. “The only kind of people I want counting my money are short guys that wear yarmulkes every day.” After his cabal of conspiracy theorists forced Barack Obama to present his birth certificate, Trump demanded the president’s college grades (offering $5 million in exchange for them), insisting that Obama was not intelligent enough to have gone to an Ivy League school, and that his acclaimed memoir, Dreams From My Father, had been ghostwritten by a white man, Bill Ayers…